This invention relates to medical diagnostic equipment and more particularly to an ultrasound imaging method and apparatus.
Linear arrays have been used in ultrasound imaging for many years. The elements of the array are operated successively to produce parallel scan lines in a plane parallel to the length of the array. Bom U.S. Pat. No. 3,789,833, which issued on Feb. 5, 1974, discloses such a linear array.
Mechanical sector scanners have also been used in ultrasound imaging for many years. A single ultrasound element is repeatedly operated as it oscillates back and forth to produce divergent scan lines in the plane of oscillation. Examples of such mechanical sector scanners are disclosed in Finsterwald et al U.S. Pat. No. 4,426,886, which issued on Jan. 24, 1984, and Matzuk U.S. Pat. No. 4,092,867, which issued on June 6, 1978.
Ultrasound transducers that combine a linear scan and a sector scan are also known. For example, Goldstein U.S. Pat. No. 4,817,616 discloses a prostate probe that has a support member on which a pair of ultrasound transducers are mounted in longitudinally spaced relationship along an axis. One transducer is a linear array and the other transducer is a mechanical sector scanner. The transducers are oriented to scan different orthogonal planes of an object under study. A shifting mechanism moves the transducers one at a time into a unitary scanning position and actuates the transducer in the scanning position to scan the object under study.
Ledley et al. U.S. Pat. No. 4,798,210 discloses a three dimensional imaging system. In one embodiment, a plurality of ultrasound source-detectors are rotatably driven by a motor to form sector scans. As the source-detectors rotate, successive transmissions of ultrasound energy take place in directions displaced by increasing angular amounts.